Fastener designs for securing work pieces together, such as, for example, a top laminate non metal work piece to a bottom light-gauge metal substrate (18 gauge and thinner) or alternatively, a light-gauge metal work piece to light-gauge metal substrate have generally been accomplished by threaded fasteners. The helical design of the thread has been successful in pulling the top laminate materials together tightly with the light-gauge metal substrate. Additionally, the helical thread design has provided sufficient withdrawal resistance to achieve performance values acceptable to industry. However, installation of helical threaded fasteners has proven time-consuming and fatiguing to the installer. The industries using these light-gauge metals require a fastener that has the speed of pneumatic nailing system with the gripping and clamping features of helical-thread fasteners.
Nail-like products (hardened pins) have been used successfully in attaching work pieces (including top metals) to heavier gauge metal substrates (16 gauge and thicker). However, when the metal substrate is of light-gauge metal (18 gauge and thinner) or two more pieces of light-gauge metal (18 gauge and thinner) are to be joined together, the substrate may be pushed away (deflection) from the top piece before the penetration and fastening process is completed. Additionally, the thinness of these metals is such that is creates situations where there is insufficient material to provide a friction-lock for current state-of-the-art pins. Whether they incorporate barbs, protrusions, undercuts, cross-hatching or spiral threads, these hardened pins lack withdrawal resistance when installed in these light-gauge materials. Additionally, they lack the ability to pull the substrate and the work piece together to close the gap between them caused by the deflection when the metal substrate is of light-gauge metal.
L. H. Flora (U.S. Pat. No. 2,740,505 and U.S. Pat. No. 2,751,052), discloses a one-piece, spring steel roofing nail for attaching insulation to a sheet metal deck. This roofing nail incorporates a center tongue within a cutout of the body, a point piercing the light-gauge metal deck, and a head, bent in an angle from the same material as the body, used for clamping of the insulation layer. The body includes elongate ribs which are incorporated to stiffen and ridgify the body. In Dimas (U.S. Pat. No. 3,983,779), such ribs are also incorporated but are formed in a more arcuate manner than an acute bend. McChesney (U.S. Pat. No. 1,934,134) also discloses a fastener in the form of a tack for holding two pieces of wood together. This tack is formed from a continuous strip of flat wire which is swaged on both side edges to form converging side flanges which provide a wedge shaped appearance to the width dimension of the web between the side flanges. The provision of such ribs or side flanges dramatically increases driving forces necessary for installation of the nail. In the low-density laminate (insulation) for which both Flora and Dimas have developed their roofing nail and wood for which McChesney developed his tack driving resistance may not be a problem. However, when denser laminates (i.e., gypsum board, plywood, oriented-strand board, cement board) are being fastened to a metal substrate, driving forces encountered are of such nature as to possibly cause incomplete installation. When a commercial pneumatic tool is used for power installation, these added driving forces are enough to “stall-out” the tool. In accordance with the principles of the present invention, for successful fastener installation using a commercial power tool through work pieces of denser material than insulation, the fastener body should be of a design having minimal driving resistance. As a result stiffening ribs or any other protrusions from the plane of the body should be avoided.
It has also been discovered that power installation of a fastener can exceed the driving forces available from the power tool if the maximum thickness of the body is engaged at the beginning of the penetrating point. Therefore, a gradual increase of the body thickness is required from the point up to some substantial area of the body where maximum body thickness is achieved. This “wedge” shape in the thickness dimension allows a progressive opening of the depth of the pierced hole, thereby allowing driving forces to remain within the power curve of a power installation tool. However, the “wedge” shape of the body with material removed to create a void for a tine (as in the design of the present invention) would create a body too weak to withstand driving forces required for installation. Therefore, corresponding stamped depressions (coining) running the majority of the length of the body are required for additional body strength. These strengthening characteristics must all be recessed below the main body surface as not to cause driving resistance such as encountered with the prior art side stiffeners. Any protuberance beyond the surface of the body, except for the tine, acts as driving resistance and can adversely affect proper installation.
Additionally, it has been found that a continuous beveling of the side edges of the body including the penetrating point side edges is a major aid in reducing driving forces. Also, the V shaped point having beveled side edges has been found to be beneficial in penetration.